Gas-detector.



A. B. LAMB AND c. R. HOOVER.

GAS DETECTOR.

APPLICATION FILED DEC.

' Patented Nov sTATEs PATENT oEEIcE.

B. LAMB, 'OF UNITED STATES ARMY, AND CHARLES R. HOOVER, 0F

MVIDDLETOWN, CONNECTICUT.

Gas-numeros. l

Speoication ot Letters Patent.

Patented Nov. 4t, tfg.

To all 'whom t may concern:

Be it known that we, Lieut. Col., and CHAnLEs -R. HoovER, civilian,Chemical Warfare Service, U. S. Army, citizens of the United States, andresiding at 'Washingtom D. C., and Middletown, Connecticut,respectively, have invented certain new and useful Improvements inGas-Detectors, of which the following is a specification.

This invention relates to methods of and means for detecting oxdizablegases such as carbon monoxid, ars'in, phosphin, ammonia, and manyothers, and also relates specifically to methods of and means fordetecting small quantities of carbon monoxid.

One of the objects of the invention is to provide a compact andself-contained unit for the detection of the above gases, one that canbe used for the detection of harmful gases in mines, industrial plants,etc.

The invention consists in making use of a very sensitive form of thematerial described and claimed by us in application Serial No. 268,750,filed concurrently herewith, in such manner as to permit the observationof the color change characteristic of the material and in such manner asto allow the material to undergo this change only in the presence of aparticular gas.

Detectors prepared in accordance with the present invention are shown inthe accompanying drawings in which the figures show two types ofprepared units for the detection of carbon monoxid, Figure 1 showing thearrangement of the materials in a single tube and Fig. 2 showing asimilar arrangement of materials but having the several materials inseparate and detachable tubes, so that any one of them may be removedand a fresh one substituted when it is considered necessary.

In the codepending application above referred to, there are describedprocesses of making a material which, for want of a better name, hasbeen named hoolamite. The composition of the material varies somewhataccording to the purpose for which it is to be used, but only in theproportions of the several constituents. The nal product is a mixture orcompound, or both, of oxids of iodin, oxids of sulfur, and water. Theremay be added to this a small amount of iodin and a solid supportingsubstance,

ARTHUR B. LAMB,

solid supporting material may be pumice or asbestos 'but it should beunderstood that any suitable material may be used in the place of these.

In the preparation of the new product, fuming sulfuric acid and iodcanhydrid are used in proportions varying from a small amount of one in arelatively large amount of the other to a relatively large amount of thefirst with a small amount of the second. The most advantageous mixturesfor most purposes, however, lie in the range of from 3 to 1v of the acidto l to 10 of the iodic anhydrid, The particular proportlons to bechosen will depend upon the use. For example, in respirators, it isdesirable to use a composition having not too great a proportion offuming sulfuric acid because of the tendency to give oil' sulfuricanhydrid. For other purposes it may be that a small amount of sulfuricanhydrid in the gas after treatment will not be objectionable and insuch cases a greater proportion of the acid my be used with an increasein the sensitiveness of the composition.

In these processes involving the use of pumice as a carrier it has beenfound to be an advantage to heat the pumice immediately before mixing,as this allows a better mixing and produces a somewhat better product.

Instead of first mixing the acid and umice with the subsequent additiono the iodic anhydrid, the latter may be thoroughly mixed dry with thepumice and the fuming sulfurid acid then added and the whole mixed untiluniform.

Further, instead of proceeding in the manner indicated in the lastparagraph, the iodio anhydrid may be prepared for reaction by saturatingthe granular or fragmentary carrier with iodio acid in water,evaporating to dryness, and continuing the heating to dehydrate theacid, leaving iodio anhydrid on the carrier. This is then mixed with thefuming sulfuric acid as before indicated.

In case a solid product without a support is desired, about equal partsof iodio anhydrid and fuming sulfuric acid are allowed to interact at aslightly elevated temperature or allowed to stand in contact for a fewdepending upon the use of the product. The

vdays until a. hard uniform product is obtained. This is then broken inpieces ofthose cases where a larg? proportion of fuming sulfuric acidhas een used and when acting as an oxidizing agent undergoes a colorchange from White to green to brown. This color change is not permanentbut dis.- appears on standing and the material may be repeatedly reuseduntil the iodic ox1d has been entirely reduced. It is strongly corrosiveand therefore should be kept in containers of glass, porcelain, etc. t

The material prepared in the manner dicated in the above mentionedapplication may be modied as to its sensitiveness by the varia-tion ofthe amounts of the constituents, as indicated in the description.

In general, the oxidizing absorbent is repared by thorough mixing ofiodic anhy .rid and strong fuming sulfuric acid with orwlthout theaddition of a carrying material, such as asbestos ory pumice, dependingupon whether the constituents are so proportioned as to produce a liquidor a solid product. In some cases a liquid product is desirable, but, inmost cases, if the product is a liquid, it must be absorbed in-such acarrier as above mentioned in order that gases may be suiti ably'contacted therewith, such as by passing them through it.

In making up a product to be used in detecting small amounts ofoxidizable gases mixed with large quantities ofv diluting gases,it isnecessary to so proportion the constituents as to give a very sensitiveproduct. This is done by increasing the proportion of the fumingsulfuric acid, as, within certain limits, the greater the proportion ofthe fuming sulfuric acid, the more sensitive the product.

As a specific example ofthe preparation of a product which is suitablefor use in the detection of, e. y., carbon monoxid, the following methodis given:

30 parts4 of pumice stone, freed from organic matter and water byyignition, and passing through a 2O mesh but retained by a 40 meshscreen, are treated with 50 parts of fuming sulfuric acid, sulfurtrioxid and after thorough mixing, 10 parts of iodic anhydridare addedand thoroughly mixed. The product isa white granular solid.

In order to increase the lsensitiveness it 1s sometimes advanta eous toadd a small proportion of iodin, grom .25 to 2% being sufficient.

Material prepared in this method reacts In choosingv proportions of theconstituents for the purposeofmaking a' detector which will make thecolor change more pronounced, .e., the material should be sulicientlyWhite to enable one to easily perceive the green tinge caused by a smallamountof oxidizable gas..

.In using the above material for the detection of oxidizable gases it isonly necessary to pack someI of the material in a glass tube and passthe gases therethrough, whereupon the presence of the oxidizable gaseswill cause the characteristic color change to green and if in sufficientquantity, to

brown. It is better, however, when making use of the material, toprotect it from the moisture usually present and this may bel done 'byplacing in the tube on either side of the material, a drier such aspumice in which has been absorbed sulfuric acid.

A more specific application of the material is its use in the detectionand approximate estimation of the carbon monoxid, present in gasmixtures. This use may be carried out by preparing a tube containing alayer of active charcoal or other suitable absorbent and a layer of theoxidizing absorbent material and passing gases through the tube in suchmanner that they pass through the charcoal first and in measuring theamount passed. The charcoal will absorb from the gases substantially allof the oxidizable gases except carbon monoxidtand hydrogen and. thelatter will not react With 'the material. As the color change of thematerial is un'rform and gradual, the extent of the change will indicatehow much carbon monoxid has been acted upon.

It is, of course, evident that tubes containing the several substancesmentioned may be previously prepared andused singly or togethervasindicated above. y

In the drawings there are shown two 'suitable arrangements of apparatuswhich may be used for the detection and approximate estimation of carbonmonoxid.

The device shown in Fig, 1 is one not intended to be renewed after oncehaving been exhausted. That of Fig. 2 is one in which the several partsmay be detached and fresh elements substituted therefor. y

In Fig. 1, A is a glass tube having a reduced portion at one end andhaving packed ite in the following fashion: First, there 1s`a smallamount of granular pumice B or equivalent materlal, such as glass woolor .therein charcoal, a drier, and the hoolamsealed ofi".

asbestos. This pumice or other material is used for the purpose ofretaining the granular charcoal C which is used for the purpose ofabsorbing other oxidizable gases than carbon monoxid. Next in order inthe tube is the layer of drier D which is preferably though notnecessarily sulfuric acid absorbed by granules of pumice. In the reducedportion of the tube there is placed the hoolamite in granular form E andthe ends of the tube In using the tube of material thus pre-` pared, itis only necessary to break oif the tips of the tube and` forcethe-suspected gas mixture through the tube and materials in the orderabove indicated. If the gas contains carbon monoxid, the color ofv thehoolamite changes in the characteristic manner.

In Fig. 2 the several elements of the detector are made detachable, aform more convenient for some purposes. This form of the detectorconsists of a small glass tube of the hoolamite H, one end of which maybe thrust through the stopper Kwhich its in the end of the tube Fcontaining the granular active charcoal M. This charcoal is suitablyretained in position in the tube by the porous plugs N and the spring L.In the other end of the tube- F is inserted the delivery end of the bulbO' adapted to force air or other suspected gas through the tube and thematerials.

It is to be understood that the invention is not to be limited to thespecific examples herein given as it is obvious that these may be variedwithout departing from the spirit v of the invention as defined intheaccompanying claims. i

Claims:

1.v A means for detecting and estimatin carbon monoxid in gas mixtures,comprising a layer of active charcoal, a layer of hoolamite, means forpassing the gases through the layers in the order named, and meanspermitting the observationof the change in color of the hoolamite.

2. A means for detecting the presence of oxidizable gases in mixtures ofgases, comprising a layer of a drying material and .a

layer of hoolamite and means for permitting the observation of the colorchange in the hoolamite.

3.Y A means for detecting and estimating carbon monoxid in gas mixtures,comprising a glass tube containing a layer of active charcoal and alayer of hoolamite and means for passing the gases through the tube andlayers in order named.

4. A means for detecting the presence of oxidizable gasesin mixtures ofgases, comprising a glass tube containing a layer of drying material anda layer of hoolamite and means for passing the gas mixture through thetube and layers in the order named;

5. Means lfor detecting the presence of oxidizable gases in gasmixtures, comprising a tubular element wherein are arranged layers ofhoolamite, a drier, and a selective absorbent in such fashion as topermit passing the gas mixture therethrough in the reverse of the ordernamed.

6. Means for detecting the presence of carbon monoxid in gas mixtures,comprising a separat@J container for bodies of granular active charcoaland a drier, means whereby the gas mixtureJY may be passed through thesaid materials in series, and means containing a body of hoolamite soarranged as to allow the passage therethrough of the gas mixturepreviously passed through the drier and charcoal.

7. Process of detecting the presence of carbon monoxid in gas mixtureswhich comprises passing the mixture through an absorbent capable ofremoving therefrom other oxidizable gases than carbon monoxid and thenpassing the residual gases through a body of hoolamite, the presence ofcarbon monoxid being shown by the change of the color of the hoolamite.

8. Process of detecting the presence of oxidizable gases in gasmixtures, which comprises passing the said mixtures through a drier andthen through a body of hoolamite, the presence ofl the oxidizable gasesin the mixture being indicated by a change of color of the hoolamite.

ARTHUR B. LAMB. CHARLES R. HOOVER.

